The structural monitors in the command vault had begun to record a series of "Micro-Shunts"—minute, grinding shifts in the limestone bedrock that occurred every time the Deep-Rail cable reversed its load. The mountain was nearing its physical threshold. By hollowing out eleven tiers to house nearly a thousand people and their industrial machinery, Kael had removed the very mass that kept the Salt-Spur ridge stable. To prevent a catastrophic "Structural Slump," he initiated the Iron Skeleton: a project to replace the mountain's organic strength with a coordinated network of high-tensile iron buttresses.
The technical core of the project was the Rib-Vaulting System. Kael utilized the foundry's newest output: massive, curved I-beams forged from the manganese-iron alloy. These ribs were designed to follow the natural contour of the largest galleries, spanning from the floor to the apex of the ceiling. Instead of relying on the stone to hold itself up, the mountain would now lean on a skeletal frame that could flex under the weight of the overburden.
"We aren't just shoring up a mine," Kael told the expansion brigades. "We are turning the mountain into a machine. These ribs will be connected by tension-rods that run through the pillars. When the stone tries to expand or settle, the iron will pull back. We are giving the mountain a nervous system of steel."
The grit of the installation required a level of precision that tested the Master Gauges. Each rib segment weighed over two tons and had to be hauled into place using steam-powered winches. To anchor them, the Tier 0 laborers and the Aspirant smiths had to drill "Lock-Socket" holes eight feet deep into the limestone using the rotary bore. These sockets were then filled with a mixture of molten lead and iron-filings, "welding" the skeleton directly into the bones of the earth.
Socially, the Iron Skeleton project was a visible manifestation of the barony's permanence. As the massive iron arches rose in the common halls and the residential corridors, the citizens felt a renewed sense of security. The "Mirror-Readers" noted that the rhythmic grinding noise that had haunted the lower tiers for weeks had been replaced by a low, stable hum. The mountain no longer sounded like it was breaking; it sounded like it was braced.
A structural failure occurred during the reinforcement of the Tier 5 Foundry Hall. As the primary rib was being tensioned, a hidden "Vug"—a hollow pocket in the limestone—collapsed behind the anchor point. The sudden shift caused the iron beam to twist, snapping the high-tension rods with a sound like a lightning strike. The ceiling began to shed "spall"—jagged shards of stone that rained down on the forge floors.
Kael utilized the "Grout-Jacking" method. He halted all movement in the tier and redirected the high-pressure lime-slurry pumps from the old bridge-work. He injected the pressurized grout directly into the vug, filling the void and creating an artificial stone "pad" for the anchor. Once the grout cured under the heat of the foundry, the rib was re-tensioned, successfully "jacking" the ceiling back into its original position and sealing the fissure.
The engineering of the Iron Skeleton allowed for the population to continue its climb. As the primary supports were finalized, the sense of "Limestone Creep" vanished. The mountain was now capable of supporting at least twenty more tiers.
Kael stood at the base of a massive arch in the central hub, his hand feeling the slight, cold vibration of the iron. He looked at the updated population logs. The count had reached 965. The influx of refugees from the northern hills had slowed, but the internal growth—the first generation of children born within the stone—was beginning to add to the numbers.
"The frame is solid, Elms," Kael said, watching the light of the arc-lamps reflect off the manganese steel. "We've secured the house. But a house of a thousand people needs a 'Standardized Language' of information. Our acoustic pipes are clogged with too many voices, and our telegraph lines are a mess of tangled copper. To manage a city, we need to move from sound to 'Logic.' We need to start the Relay-Brain."
Kael began the designs for Tier 13: The Logic Vault—a central switching station where a series of mechanical relays and steam-driven logic gates would automate the mountain's resource distribution.